In humans and other vertebrate animals, the heart is hollow muscular organ having four pumping chambers separated by four heart valves: aortic, mitral (or bicuspid), tricuspid, and pulmonary. The valves open and close in response to a pressure gradient during each cardiac cycle of relaxation and contraction to control the flow of blood to a particular region of the heart and/or to blood vessels (pulmonary aorta, etc.)
These valves are comprised of a dense fibrous ring known as the annulus, and leaflets or cusps attached to the annulus. For some valves, there is also a complex of chordae tendinae and papillary muscles securing the leaflets. The size of the leaflets or cusps is such that when the heart contracts the resulting increased blood pressure formed within heart chamber forces the leaflets open to allow flow from the heart chamber. As the pressure in the heart chamber subsides, the pressure in the subsequent chamber or blood vessel becomes dominant, and presses back against the leaflets. As a result, the leaflets or cusps come in apposition to each other, thereby closing the passage.
Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Diseased heart valves may be categorized as either stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, and/or incompetent, wherein the valve does not close completely, causing excessive backward flow of blood through the valve when the valve is closed. Valve disease can be severely debilitating and even fatal if left untreated. Various surgical techniques may be used to repair a diseased or damaged valve. In a traditional valve replacement operation, the damaged leaflets are typically excised and the annulus sculpted to receive a replacement prosthetic valve.
In many patients who suffer from dysfunction of the mitral and/or tricuspid valves(s) of the heart, surgical repair of the valve (i.e., “valvuloplasty”) is a desirable alternative to valve replacement. Remodeling of the valve annulus (i.e., “annuloplasty”) is central to many reconstructive valvuloplasty procedures. In 1968, Dr. Alain Carpentier published studies which demonstrated that such remodeling of the valve annulus might be accomplished by implantation of a prosthetic ring (i.e. “annuloplasty ring”) to stabilize the annulus and to correct or prevent valvular insufficiency that may result from defect dysfunction of the valve annulus. The annuloplasty ring is designed to support the functional changes that occur during the cardiac cycle: maintaining coaptation and valve integrity to prevent reverse flow while permitting good hemodynamics during forward flow. Annuloplasty procedures are performed not only to repair damaged or diseased annuli, but also in conjunction with other procedures, such as leaflet repair.
The annuloplasty ring typically comprises an inner substrate of a metal such as stainless or titanium, or a flexible material such as silicone rubber or Dacron cordage, covered with a biocompatible fabric or cloth to allow the ring to be sutured to the heart tissue. Annuloplasty rings may be stiff or flexible, may be split or continuous, and may have a variety of shapes, including circular, D-shaped (including kidney-shaped), or C-shaped. Examples are seen in U.S. Pat. Nos. 4,042,979; 4,290,151; 4,489,446; 4,602,911; 5,041,130; 5,061,277; 5,104,407; 5,201,880; 5,258,021; 5,607,471; and 6,187,040, the contents of each of which is hereby incorporated by reference in its entirety.
For some patients, the condition of the native heart valve requires complete replacement using a prosthetic heart valve. Prosthetic heart valves have been known for some time, and have been successfully implanted using traditional open-chest surgical approaches. Sometimes the need for complete valve replacement may arise after a patient has already had a repair using an annuloplasty ring. For example, a native heart valve that was successfully repaired using an annuloplasty ring may suffer further damage years after the annuloplasty ring was implanted.
Implanting a prosthetic heart valve into a patient with a previously-implanted annuloplasty ring typically involves additional steps from a similar procedure in a patient with no annuloplasty ring. Implanting the prosthetic heart valve directly within a previously-implanted annuloplasty ring is generally impractical, largely because most prosthetic heart valves have a generally circular shape whereas most annuloplasty rings are generally non-circular (including “D” and dog-bone shapes). Implanting a prosthetic heart valve in a patient who previously had an annuloplasty ring generally requires the annuloplasty ring to be removed during the same procedure in which the prosthetic heart valve is implanted. In such cases, a surgeon can use a traditional surgical approach to install the prosthetic valve, which can involve the surgeon cutting out the native valve as well as the previously-implanted annuloplasty ring from the heart valve annulus, and then implanting the prosthetic valve into the heart valve annulus.
Percutaneous heart valve replacement has been developed recently, wherein a prosthetic heart valve is advanced percutaneously (e.g., via the femoral artery or other desired approaches) into the heart valve annulus, and then expanded within the heart valve annulus. Percutaneous heart valve replacement is often performed without cutting out the native heart valve, wherein the prosthetic heart valve is expanded in the native heart valve annulus and the native valves are pressed against the valve annulus walls by the expanded prosthetic heart valve. However, in cases where a previously-implanted annuloplasty ring is present, deploying a prosthetic heart valve within the native heart valve may be impractical. The general non-circular shape of the annuloplasty ring may not be compatible with the (typically) circular configuration of the percutaneous prosthetic heart valve, and the annuloplasty ring shape and structure may interfere with the proper placement, deployment, and functioning of the prosthetic heart valve.
Although some of the annuloplasty rings of the prior art have incorporated means for adjusting the shape and size of the ring at the time of implantation, the inventors are aware of no prior art annuloplasty ring constructed and equipped for post-implantation shape change to accommodate and even assist implantation of an expandable heart valve within the heart valve annulus and annuloplasty ring. There is thus a need for an annuloplasty prosthesis and implantation device which will properly reshape/repair a damaged heart valve, but will also enable a prosthetic heart valve to be deployed therein at a later time. The current invention meets this need.